The present invention refers to targets devices used for simulating of various military and civilian objects, like armored fighting vehicles, battle tanks, armored personnel carriers, military and civilian vehicles. The invention also refers to identification and marking means used for identification of those objects.
The products of the invention are intended mainly but not solely for activities associated with improvement the combat effectiveness of military forces, e.g. gunnery training, friend or foe target recognition and identification training, battlefield simulating and other activities.
The present invention refers to multi-spectral products including targets and identification means capable to simulate both the thermal and visual detectable signatures of various military and civilian equipment and to allow its detection and recognition either in darkness or in the daytime.
There are known various military targets, which have been devised for simulating of military assets and intended for use in so-called cover, concealment and deception (CCandD) activities.
The existing military targets used in CCandD activities can be divided into three groups according to the principle of their operation.
The first group includes military targets, which are detectable and recognizable during the day only. An example of such a target is inflatable target apparatus, disclosed in U.S. Pat. No. 4,505,481. This apparatus simulates battlefield and comprises an inflatable target mounted on a trolley. The inflated target is suitable for detection the passage of a projectile. The disadvantage of this group of targets, associated with their limitation strictly to daylight is self-evident.
The second group of targets includes so-called thermal targets, i.e. those, which are detectable and recognizable at night. These targets when heated emanate infrared radiation, known as object""s thermal signature. A sighting device or so-called thermal image capable to detect infrared radiation at night or can see the thermal signature in conditions of obscured visibility.
The main disadvantage of these targets is associated with the fact, that they necessitate an external source of energy, capable to heat the target and to induce the infrared radiation. For the sake of brevity, such thermal targets will be referred-to further as active thermal targets.
An example of such active thermal target can be found in U.S. Pat. No. 5,065,032, disclosing thermal integrated target that produces and emits an infrared image for simulating heat emitting equipment or personnel. The image is formed when an electric current passes through a resistive coating applied to the target. This integrated target is intended for use at night only.
Another example of an active thermal target for night vision is described in U.S. Pat. No. 4,260,160. This thermal target is intended for practice shooting in darkness and it comprises a thin supple fabric supported on a rigid frame. The configuration of the fabric simulates the silhouette of an object at which firing would take place, e.g. a tank as seen from its front. The fabric comprises a front protective sheet and a rear radiation-absorbing sheet. The front sheet is held spaced and parallel from the fabric and thus a heat insulating space is defined between them. An infrared radiator heats the heat-absorbing sheet, which radiates as a black body. By virtue of this provision a heat radiation pattern is produced, which closely simulates the object. The disadvantage of this target is similar to that mentioned in connection with U.S. Pat. No. 5,065,032.
The third group includes active thermal targets, which can be used also during the daytime. Those targets are known as multi-spectral targets.
An example of such thermal target is disclosed in U.S. Pat. No. 5,599,023 referring to partially translucent mural decoy. This decoy contains selective translucent panels representing horizontal and other areas of the simulated target. By virtue of this provision, the target represents the object realistically during the day irrespective of the incidence of sunlight to the object. The decoy can be also provided with an auxiliary means for supplying warm air into a bag disposed on one said of the target. By virtue of this provision, the decoy appears warm under infrared observation and therefore is detectable at night.
Even more sophisticated multi-spectral active thermal target is disclosed in U.S. Pat. No. 4,422,646. In this patent, there is described infrared target for military applications. The target comprises a multiplicity of independent modules, each of modules corresponding to a thermal cue of a military object. Each module comprises flexible laminate capable of conducting an electric current, supplied from an external electrical power source. The top layer of the laminate is covered by a flexible, thermal insulating pad containing a multiplicity of discrete air-containing cells through which an infrared signal can pass. The modules are covered by visible graphics to depict the object in visible light and thus the visual signature of the military object is superimposed upon the thermal signature. Nevertheless, by virtue of the cells the thermal signature can be radiated and seen at night through the visual signature.
The active multi-spectral targets are good for recognition of a simulated object. Nevertheless, their sufficient intrinsic disadvantage is the necessity in an auxiliary source of heat energy, which should be sufficient for producing reliably detectable and recognizable thermal signature. Active targets require relatively large amount of electrical power, they are difficult to control, their construction is complicate and they are relatively expensive items.
There are also known so-called low emissivity thermal coatings, which exhibit very low emissivity in the thermal infrared band range. When such a coating covers some areas of an object, the intensity of the infrared radiation, emanated by the coated areas is much lower in comparison with the intensity of the infrared radiation emanated by the uncoated areas. This phenomenon allows using such coatings for thermal insulation applications, in particular for insulation curtains of windows.
Insulation products, based on low emissivity coatings are manufactured for example by Hanita Coatings, Israel. These products comprise sandwiched structure, consisting of several thin aluminum layers interspersing with polyester film layers. A low emissivity lacquer, having emissivity 0.22-0.29, coats the upper aluminum layer. Such sandwiched structure reflects more than 70% of the radiation in the several micron band ranges and provides reliable thermal insulation.
By virtue of low emissivity insulation coating a thermal contrast can be created, enabling detection and recognition within the IR specter of those areas, which were hidden by the coating. The hidden areas of an object will be seen in a thermal imager as xe2x80x9ccoolxe2x80x9d regions, contrasting with the adjacent xe2x80x9chot xe2x80x9d regions, corresponding to the uncoated areas. It can be easily appreciated, that this thermal contrast can be induced without heating of an object and thus without the necessity to employ an external source of thermal energy.
The targets based on this approach include so-called passive or no-power targets and they refer to the fourth group. These targets are manufactured for example by Opticoat Associates Inc. U.S.A.
A target employing low-emissivity coating is disclosed in U.S. Pat. No. 3,986,384. This target is used for testing infrared sensors and provides a known spatial pattern such as a bar group. In order to provide a passive target, which is suitable for a range of thermal contrasts the target is formed as a sandwiched structure, consisting of three plane rigid members. The intermediate member is incrementally slidable between the front and rear member. The front member has a cutout, which exposes the intermediate member and the intermediate member has a perforated region in the area exposed by the cutout. The perforations expose the rear member.
The surface of the front and intermediate member is coated by a pattern painted by high emissivity paint (black) and the surface of the rear member is coated by a pattern painted by low emissivity paint. That region of the rear member, which is behind the perforations is coated by a pattern identical with a perforated region of the intermediate member and is painted by high emissivity paint. By incremental sliding the intermediate member between the front and rear member, it is possible to vary the contrasts of the pattern visible on the front member.
Additional applications of military articles, employing low emissivity coatings include so called boresight panels for testing infrared sensors to have an infrared system aligned (boresighted) with a visual system, battleground reference panels.
A boresight panel is configured as a rigid plate having white background (high emissivity object) with applied thereon low emissivity thermal tape (low emissivity object) configured as a known spatial pattern, e.g. cross or a bar group. Since the tape has bright color, it is clearly visible in the daylight. When this plate is viewed through an infrared imager the thermal signature of the tape shows up as a known spatial pattern and can be used to align the thermal IR system with the visual system. The boresight panels are used for testing advanced infrared sensors and they are not suitable for gunnery training.
Battleground panels are used for identification, as resolution test boards, camouflage panels, camouflage battle boards, etc. In these panels, a high emissivity rigid substrate carries stripes of a tape on top of it. When the panel is viewed through an infrared imager, the low emissivity stripes are easily resolved and are distinctive.
The above-mentioned passive targets, provided with low-emissivity coatings are suitable for thermal and visual detection, classification, recognition and identification training associated with testing and alignment of imagers. Unfortunately these targets are not intended for such applications, like live gunnery training, since they are not designed to represent an image of a military asset during the day and its thermal signature at night. The known passive targets represent merely special spatial pattern, which visual and thermal signature should be of identical configuration. In known in the art passive targets, the low emissivity pattern resides on the high emissivity visual pattern and hides thereof. Therefore visual detection and recognition of the image can be difficult and therefore such targets could not be used during the daytime.
Furthermore, the known in the art passive targets are rigid flat structures, their construction is rather sophisticate and it cannot be folded or rolled up into compact configuration, suitable both for convenient storing and rapid set up.
In conclusion it should be emphasized that despite the fact that different visual and thermal targets have been devised there is still exists a need in a new and improved target, which will enable good and reliable representation of various assets, detectable and recognizable round the clock.
The object of the present invention is to provide a new and improved multispectral products including no-power target and identification means, which sufficiently reduce or overcome the above-mentioned drawbacks of the known in the art targets and identification means.
In particular, the main object of the present invention is to provide a new and improved target and identification means for simulating various military or civilian assets, in which high emissivity pattern depicts visual image of an asset, which is superimposed with a low emissivity pattern, representing thermal signature of the same asset.
The other object of the invention is to provide a new no-power, passive target and identification means, in which the low emissivity pattern is hidden by the visual image of the asset to enable detection and recognition of the thermal signature without deterioration of the visual image.
The further object of the present invention is to provide a new and improved no-power target and identification means, which has very simple construction and is inexpensive.
Still further object of the invention is to provide a no-power passive target means and identification means for simulating or marking of various objects, primarily military assets. These products are suitable for fire gunnery training, simulating battlefield, friend or foe recognition training and identification, air reconnaissance training etc.
Yet, another object of the invention is to provide a versatile no power, passive target and identification means, which reliably represents visual image of either three-dimensional or two-dimensional objects.
Still further object of the invention is to provide a new and convenient target and identification means, which is lightweight and may be easily and rapidly deployed or folded without special tools.
The above and other objects and advantages of the present invention can be achieved in accordance with the following combination of its essential features, referring to different embodiments thereof.
According to one of the preferred embodiments, the target and identification means of the invention is formed as a sandwiched structure comprising:
a rear layer, carrying the structure,
a front layer, covered by two-dimensional pattern rendering the simulated object visually detectable and
an intermediate layer, overlapping with at least a portion of the front layer, said intermediate layer is capable to simulate thermal signature cue of the object,
wherein said front layer is made of a discontinuous material, provided with multiplicity of openings passing the infrared radiation therethrough in order to render said thermal signature cue detectable in darkened conditions by virtue of thermal contrast, while preserving possibility for recognizing the simulated object in visible light.
According to the other embodiments the front layer is made of non-wetting, meshed fabric.
In accordance with the further embodiment, the meshed fabric is made of knitted polyester.
The fabric could be coarse meshed net made of artificial material, e.g. high-density polyethylene.
In accordance with still further embodiment the intermediate layer is made of a polyester sheet coated by a low emissivity thermal coating. The coating has heat reflection of at least 0.7 and renders thermal signature cue detectable by virtue of thermal contrast.
The present invention in its various embodiments has only been summarized briefly.
For better understanding of the present invention as well of its advantages, reference will now be made to the following description of its embodiments with reference to the accompanying drawings.